Change an image’s dimensions

In the Preview app on your Mac, if the Markup toolbar isn’t showing, click the Show Markup Toolbar button , then click the Adjust Size button .

Enter new values for width and height, or click the “Fit into” pop-up menu and choose a size.

Resize the image by a percentage: Choose “percent” from the pop-up menu next to the Width and Height fields, then enter the percentage in those fields.

Force the image to keep its original proportions: Select “Scale proportionally.” If you change either the width or height, the other value changes to maintain the proportions. If you choose a size from the “Fit into” pop-up menu, the image’s width or height may be smaller than the chosen size to maintain the proportions.

Make the image’s dimensions smaller without losing any detail: Deselect “Resample image” before changing the width or height.